1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus comprising a magnetic head having a main magnetic pole, a magnetic recording medium, and a drive device body that can operate to rotationally drive the magnetic recording medium in a constant direction and cause the magnetic head to be movable in radial directions of the magnetic recording medium. The magnetic recording medium concerns a magnetic recording medium of a so-called discrete type in which a perpendicular magnetic recording layer is formed on a substrate so as to be divided into many recording elements in a predetermined convex-concave pattern.
2. Description of the Related Art
Improvement in areal recording density of magnetic recording mediums such as hard disks has conventionally been achieved by techniques of both (1) improving the linear recording density and (2) improving the track density. In order to achieve further and higher densification in future, it is necessary to improve the areal recording density based on the foregoing both techniques.
With respect to improving the track density, there have been raised problems of processing limitation about magnetic heads, side-fringe or crosstalk caused by expansion of magnetic fields of magnetic heads, and so forth, and therefore, it can be said that the improvement in areal recording density by progressing the track-density increasing technique for magnetic heads, which is merely an extension of the conventional improvement technique, has reached the limit.
On the other hand, as a technique of improving the linear recording density, reduction in layer thickness and higher coercive forces have been achieved in conventional longitudinal magnetic mediums. However, in terms of further and higher densification of the mediums and stability of recording magnetization against thermal fluctuation, attention has been paid to perpendicular magnetic recording mediums.
Under these circumstances, as a technique of improving the areal recording density and supplementing the higher track densification of the magnetic heads, there have been proposed magnetic recording mediums of a discrete track disk type in which a recording layer is formed in a predetermined convex-concave pattern. For example, JP-A-H11-328662 discloses a magnetic recording medium in which predetermined convex and concave portions are formed on a substrate in advance and a perpendicular magnetic recording layer in the form of a single layer is formed along the convex and concave portions.
In general, a magnetic recording medium used in a magnetic disk drive has data areas (data tracks) for recording data information and servo areas (servo tracks) for recording tracking servo information and, in the case of a discrete medium, these track groups are formed as a plurality of recording elements divided in a predetermined convex-concave pattern.
The servo area generally includes an ISG (Initial Signal Gain) portion, an SVAM (SerVo Address Mark) portion, a Gray code portion, a burst portion, and a pad portion which are in the form of various magnetic patterns for exhibiting predetermined functions, respectively. Generally, in the servo area, a magnetic field is applied perpendicularly so as to carry out magnetization collectively.
On the other hand, in the perpendicular magnetic recording layer of the data area (data track), magnetic recording is carried out by a magnetic field generated in a perpendicular direction from a main magnetic pole of a perpendicular magnetic head.
A rotary actuator is normally used for driving a magnetic head. In a magnetic recording and reproducing apparatus having such a rotary actuator, assuming that, when recording/reproducing inner and outer recording tracks (data tracks) of a disk-shaped magnetic recording medium, an angle formed between a flat surface of a recording/reproducing element of the magnetic head and a plane perpendicular to a circumferential direction of a data track is defined as a skew angle and it is set to zero at a particular track, a skew angle inevitably occurs at any of the other tracks. For example, assuming that a skew angle is set to zero at an innermost data track of a disk-shaped magnetic recording medium, a maximum skew angle occurs at an outermost data track of the disk-shaped magnetic recording medium.
U.S. Pat. No. 5,995,341 discloses a technique that determines a relationship among the shape of a main magnetic pole of a magnetic head, a skew angle, a track pitch, and so on in a perpendicular magnetic recording system. This patent uses a perpendicular magnetic recording medium being a general medium not applied with discrete processing and having a continuous magnetic recording surface, specifies the shape of a tip of the main magnetic pole in cross-section as a quadrangular shape, and determines the relationship among the skew angle, the track pitch, and so on when performing magnetic recording with respect to the medium by the use of the main magnetic pole of the perpendicular magnetic head.
According to the technique disclosed in U.S. Pat. No. 5,995,341, however, although the condition is set so as to prevent the tip of the main magnetic pole having the quadrangular cross-section from overwriting in an adjacent data track, when the skew angle occurs, the writing corresponding to the skew angle is carried out in the adjacent track and, in the case of the maximum skew angle, there is no guard band so that an unwanted signal generated by bits recorded therein becomes a noise source of crosstalk. Therefore, it can be said that it is substantially impossible to effectively use the disclosed technique in the magnetic recording apparatus with such a structure. Further, this prior art is not intended for discrete mediums and a formula itself proposed therein is not applicable to discrete mediums.
In order to avoid such a problem, U.S. Pat. No. 6,504,675, JP-A-2002-92821, JP-A-2003-242607, and so on each disclose a method that uses a magnetic head having a main magnetic pole with an inverted trapezoidal cross-section and controls a recording track width so as to provide a guard band even when a skew angle occurs.
However, it is not possible to apply those disclosed techniques as they are to discrete mediums. Further, it has not yet reached the state where a substantial effect is achieved only by those disclosed techniques.
The present invention has been made under these circumstances and has an object to provide a magnetic recording apparatus that, in a mutual relationship between a discrete medium (discrete track disk) having a predetermined convex-concave structure at data tracks and servo tracks and a magnetic head having a main magnetic pole for perpendicular magnetic recording, can prevent unwanted writing into the adjacent track to thereby realize the high-density recording having extremely high reliability.